Glass manufacturing – Plural sources feeding diverse glass melts to common forming...
Reexamination Certificate
2000-09-19
2001-11-20
Derrington, James (Department: 1731)
Glass manufacturing
Plural sources feeding diverse glass melts to common forming...
C065S415000, C065S254000, C065S258000
Reexamination Certificate
active
06318128
ABSTRACT:
The present invention relates to a method and a device for the manufacture of a bar with rectangular cross section made of a material presenting a gradient of composition perpendicular to two opposite longitudinal sides of the bar and, more particularly, to such a method and a device which allow the manufacture of a glass bar having one characteristic, such as refractive index, optical density, ionic conductivity, etc., which presents a predetermined profile gradient, established as a result of a variation in its composition, perpendicular to said opposite sides of the bar.
Optical components are used today, such as lenses made of glass which presents a refractive index gradient which is parallel to the axis of the lens. To make such optical components, the starting material is a glass block whose composition varies along the axis of the component to be prepared, which variation is established using various techniques, such as ion exchange (see French Patent Application No. 2,504,515), impregnation with the so-called “sol gel” technique (see U.S. patent application No. 5,069,700), the use of starting glass compositions made of powder (U.S. patent application No. 4,883,522), the use of selectively doped porous glass (U.S. Pat. No. 4,620,861), the assembly by melting of platelets made of glass with varying composition (U.S. patent application No. 4,929,065), or other techniques such as exposure to neutron radiation, deposition of glass in the vapor phase, etc, etc.
The techniques used in the past share the feature that they apply discontinuous manufacturing processes, that is, in lots; this continuity implies downtimes which have a negative effect on productivity and thus also on the lowering of production costs. The gradients of indices obtained also were found to be insufficient in some applications and the profile insufficiently controlled.
The present invention therefore has the purpose of implementing a method and providing a device which allows the manufacture of bars with rectangular cross section made of a material which presents a gradient of composition perpendicular to two opposite longitudinal sides of the bar, and notably bars made of glass for the preparation of optical components with an axial gradient of composition, which bars present none of the above-mentioned drawbacks of the known methods and devices.
This purpose of the invention is achieved, as well as others which will become apparent upon reading the following description, with a method for the manufacture of a bar with rectangular cross section made of a material presenting a gradient of composition perpendicular to two opposite longitudinal sides of the bar, which material is in the fluid phase at a temperature above ambient temperature, and which method is characterized in that a) at least the first and second compositions of this material are prepared in the fluid phase, b) a sheet of the first composition is poured continuously on a flat support, c) a sheet of the second composition is poured continuously on the sheet of the first composition, d) the interdiffusion of the materials of the two sheets by a thermal method is ensured so as to obtain the desired gradient of composition in the cooled bar.
With the method of the invention, a bar can be prepared in a continuous process, which bar consists of a material such as glass which presents the required transverse gradient of composition, where the continuity of the method allows for of high productivity and reduced manufacturing costs.
For the implementation of this method, the invention provides a device which comprises a support which advances on a looped travel path which presents a flat part, where a number of reservoirs each receive one of the compositions of an equal number of different compositions of the material, each reservoir being equipped with means for the formation of a sheet of the material which flows by gravity from the reservoir, the reservoirs being spaced at intervals along the flat part of the travel path of the support so that said sheets flow out one above the other, above the support.
According to one embodiment of the device according to the invention, the device also comprises means for the transverse cutting of the bar formed into bar elements, heating means and means to load these elements in these heating means so as to ensure the development of the process of interdiffusion of the sheets of each element until the desired gradient of composition is established in said element.
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Gille Claude F. M.
Kerdoncuff Alain
Prassas Michel
Corning Incorporated
Derrington James
Peterson Milton M.
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